The present invention relates to fuel injection nozzles for internal combustion engines and, more particularly, to a two-stage fuel injection nozzle for concentric fuel flow from two fuel inlet lines.
Internal combustion engines, particularly diesel engines, have long used fuel injection systems for injecting fuel into combustion chambers of an engine. Air drawn into the combustion chamber separate from the fuel is mixed with a spray of fuel from the injection nozzle and ignited to create a controlled explosion for driving a piston outward of the chamber to effect rotation of a drive shaft of the engine. The power output of the engine is varied by controlling the volume of fuel injected into its combustion chambers.
In some applications, for example, in a diesel electric locomotive, the engine may have nine-inch diameter combustion chambers and be required to operate at constant speed over a broad power range. At full power, the engine may generate 4000 HP or more. At idle, the engine may only be required to generate 400 HP. The broad range of power requirements creates difficulties in injector design. The injector openings or fuel exit passages must be large enough to allow fuel flow of sufficient quantity to accommodate the maximum required horsepower. However, at minimum horsepower, the openings are so large compared to the required fuel flow that the fuel "dribbles" or "streams" into the chamber rather than being sprayed or atomized. Both the combustion pattern and efficiency of the engine are detrimentally effected by the fuel streaming at low power. Accordingly, it would be advantageous to provide an injection nozzle which could produce an atomized spray at both high and low fuel flow rates. While one solution might be a variable aperture spray nozzle, it is not believed that such a device has been developed for this type application.